1. Field of the Invention
The present invention relates to a probe block, in particular a probe block suitable for transmitting balanced signal, and a probe card and a probe apparatus both having said probe block.
2. Description of the Related Art
In recent years, with improvements in performance of semiconductor devices, it is desired to improve frequency response characteristics of inspecting apparatus which inspects electrical properties of semiconductor devices. Japanese Patent No. 2765247, for example, discloses a probe card, in which at least one probe needle is covered with dielectric film except its tip portion, and the surface of the dielectric film and conductive surfaces of other probe needles are covered with conductive substance to electrically connect them, thereby decreasing parasitic capacitance between probe needles and improving isolation between probe needles. In the probe card, however, since the probe needles are covered with the conductive substance up to the portion very close to the tip of probe needles, a movement of one probe needle affects on other probe needles. Therefore, the probe card has disadvantages that each of the probe needles is not so flexible enough to contact sufficiently with a bonding pad of semiconductor device under test. In addition, it is not so easy to assemble the probe card, because more than one probe needles have to be collected and fixed with conductive substance. On the same reasons, the maintenance of the probe card, such as exchange of probe needles, is difficult.
The Japanese Patent Kokai No. 2008-45950 (JP 2008-45950 A) discloses a probe card which uses high frequency pulse wave for inspection. The probe card basically employs coaxial structure. However, the probe card employs parallel two-wire lines structure in tip portion of the probes, because it is hard to employ coaxial structure there. The probe card thereby attempts to decrease incompleteness of impedance matching with 50 ohm. In the probe card, however, it is necessary to electrically connect a grand probe with an outside conductor of the coaxial structure. For this reason, it is not easy to assemble the probe card. In addition, satisfying high-frequency response characteristics are not achieved in the probe card, because the ground probe is different from the signal transmitting probes in its height and in its length. Furthermore, the portions having parallel two-wire structure need be fixed and supported with resin in one body at their center positions. Because of this, there are disadvantages in the probe card that installation and removal of the probes are not so easy.
The Japanese Patent Kokai No. 2008-205282 (JP 2008-205282 A) discloses a probe card, in which, among more than one probe needles, at least one of probe needles which input and output high speed signal is covered with dielectric having relative dielectric constant larger than that of air, thereby trying to relax quality control level in terms of dimensional tolerance among probe needles in high speed balanced interface. In the probe card, however, probe needles are covered with dielectric only in their parts between electrodes in circuit board of probe card and fixed positions near to the tips. Therefore, it is difficult to keep constant the space between two probe needles which form balanced transmission line, and consequently there are drawbacks in the probe card that noise is not decreased sufficiently.
The present invention has been made to overcome the drawbacks of the conventional technique as above mentioned. The aim of the present invention is to provide probes for transmitting balanced signals having superior high frequency response characteristics and being easy to be maintained. Another aim of the present invention is to provide a probe card and a probe apparatus both having said probes.